utils: fix task_blocking_signal()

src/lxc/lxccontainer.c

@@ -1829,11 +1829,10 @@ static bool do_lxcapi_shutdown(struct lxc_container *c, int timeout)
 		return true;
 
 	/* Detect whether we should send SIGRTMIN + 3 (e.g. systemd). */
-	if (task_blocking_signal(pid, (SIGRTMIN + 3)))
-		haltsignal = (SIGRTMIN + 3);
-
 	if (c->lxc_conf && c->lxc_conf->haltsignal)
 		haltsignal = c->lxc_conf->haltsignal;
+	else if (task_blocking_signal(pid, (SIGRTMIN + 3)))
+		haltsignal = (SIGRTMIN + 3);
 
 	/* Add a new state client before sending the shutdown signal so that we
 	 * don't miss a state.

src/lxc/utils.c

@@ -1769,17 +1769,16 @@ int lxc_strmunmap(void *addr, size_t length)
 
 /* Check whether a signal is blocked by a process. */
 /* /proc/pid-to-str/status\0 = (5 + 21 + 7 + 1) */
-#define __PROC_STATUS_LEN (5 + (LXC_NUMSTRLEN64) + 7 + 1)
+#define __PROC_STATUS_LEN (6 + (LXC_NUMSTRLEN64) + 7 + 1)
 bool task_blocking_signal(pid_t pid, int signal)
 {
-	bool bret = false;
-	char *line = NULL;
-	long unsigned int sigblk = 0;
-	size_t n = 0;
 	int ret;
-	FILE *f;
-
 	char status[__PROC_STATUS_LEN];
+	FILE *f;
+	long unsigned int sigblk = 0;
+	size_t n = 0;
+	bool bret = false;
+	char *line = NULL;
 
 	ret = snprintf(status, __PROC_STATUS_LEN, "/proc/%d/status", pid);
 	if (ret < 0 || ret >= __PROC_STATUS_LEN)
@@ -1790,10 +1789,10 @@ bool task_blocking_signal(pid_t pid, int signal)
 		return bret;
 
 	while (getline(&line, &n, f) != -1) {
-		if (strncmp(line, "SigBlk:\t", 8))
+		if (strncmp(line, "SigBlk:", 7))
 			continue;
 
-		if (sscanf(line + 8, "%lx", &sigblk) != 1)
+		if (sscanf(line + 7, "%lx", &sigblk) != 1)
 			goto out;
 	}